Name ANSWER KEY Slayter Box 007

Hour Examination 1 January 29, 2003

General Chemistry (CHEM 122-01)

Intermolecular Forces, Phase Transitions, Solution Properties Dr. Bennett

Please do not open until instructed

Chemistry 122-01 -- General Chemistry II Spring 2003Test #1

Intermolecular Forces, Phase Transitions, Solution Properties

Notes:

* This exam consists of 5 questions on 6 pages (including this cover page). Please check to make surethat you have a complete copy of the exam.* Please do not simply give me answers. Give me well-supported answers. Numerical answers that arenot backed by supporting calculations will receive minimal credit.* Please write clearly; if I can't read your answer, I can't give you credit for your answer.* Please note that different questions are worth different numbers of points. Plan your time accordingly.* Remember to include units and significant figures where appropriate.* No books or notes are to be used on this exam.* Please do NOT share calculators; if you need a calculator but do not have one, please let me know!

* If you feel that you would be better able to answer any question if you had additional information,please do not hesitate to ask for it. I will happily provide any information that I feel will help youanswer the question without compromising the efficacy and fairness of the test.

Question Possible Score

1 15

2 20

3 8

4 15

5 12

TOTAL 70

percent:

I have not provided any constants or formulas on this test because I did not feel that there were any thatwould be needed for the test. However, I may have overlooked something. If you were expecting to

have some quantity given to you that I have failed to provide, please let me know!

Chem 122-Bennett page 2 Test 1

1. A new substance developed in the laboratory has the following properties: normal melting point,242 °C; normal boiling point, 781 °C; triple point, 305 °C and 0.55 atm; critical temperature, 1063°C; critical pressure, 504 atm. Studies of this substance have shown the liquid phase to be moredense than the solid phase.

(a) Sketch the approximate phase diagram for this new substance given the data above. Label phasesand all important points.

(b) Make sure the slope of the liquid/solid boundary reflects the information about density. Please

describe how this information allowed you to know how to draw that line.

Chem 122-Bennett page 3 Test 1

2. Some questions about vaporization.(a) Why does the boiling point of a liquid vary with atmospheric pressure?

(b) Suggest a reason why the boiling point of isooctane is lower than the boiling point of octane.

Chem 122-Bennett page 4 Test 1

(c) Take a moment to study the diagram shown below. It is an adaptation of the mercury barometerused to measure atmospheric pressure. Three tubes are inverted in a pool of mercury. The left hand onewas filled with mercury before being inverted in the pool. Its level of mercury relative to the poolrepresents the atmospheric (or barometric) pressure.

For the second (middle) tube, the same thing was done, except that afterwards, a sample ofcompound “A” was introduced by means of a syringe, a flexible tube, and a patient experimentalist. Thecolumn of mercury moved down as some of compound “A” vaporized. The difference in levels of theliquid columns in these two tubes represents the vapor pressure of compound “A”.

An enterprising student did the same thing with compound “B” in the right-hand tube. Afterthey completed the work they were in a huge hurry to get out of lab and they forgot to draw a picture ofwhat they had observed!

The identity of the compounds was checked:A 1-propanol (CH3CH2CH2OH)B methanol (CH3OH)

Given this information, please complete the diagram as the student would have observed it.

Chem 122-Bennett page 5 Test 1

3. What is polarizability? Explain how the polarizability of krypton compares with thepolarizability of neon. How is polarizability related to strength of intermolecular attractions?

4. Consider the following pairs of chemicals. For each pair, please decide which compound wouldbe more soluble in water and briefly explain your choice.

methane (CH4) or ammonia (NH3)

butanol (CH3CH2CH2CH2OH) or butane (CH3CH2CH2CH3)

MgCl2 or CH2Cl2

Chem 122-Bennett page 6 Test 1

5. Short answer questions (explanations not required):(a) Which of the following molecules contains the most polar bond: CH4, CCl4,CH2IBr, CH3NH2,or CH3OH? (Please ask me if you need help figuring out what these molecules look like.)

(b) Which of the following molecules is the most polar: CH4, CF4,CH2IBr, NH3, or NH4+? (Please

ask me if you need help figuring out what these molecules look like.)

Also accepted ammonia

(c) Please list two fundamental molecular-scale differences between the liquid and solid states.

Other answers possible

(d) True or False: breaking some "high-energy" bonds releases large amounts of energy. (Pleaseonly consider the process of breaking the bond, not any subsequent process.)